Please can someone give me a step by step guide to lay a concrete floor for my conservatory, I'm confident I know how to do but just need reassurance, I'm also wanting to lay piping down for under floor heating, the type you connect to the radiator.

The first thing is to lay polystyrene or similar insulation, at least 4 inches thick. Heat always moves to cold and unless you prevent your heat escaping downwards the cost will be horrendous and the conservatory cold.

Having written that, take into consideration the way you will use the room.
If you intend to have the heating off most of the time, then take into account the time it will take to heat the room to a comfortable level.

Also take into account that if the room is comfortable and the sun comes out the temperature can rise suddenly needing the heating turned off.
If you have a hot concrete slab you cannot turn it off.
It will take ages to loose its heat.
Consider light weight heating like normal radiators that have a quick response time.
Consider the money you will waste in heating a block of concrete only to have breakfast and go off to work.